The present invention relates to a clockspring assembly while electrically connects a stationary housing to a rotatable hub by means of a fiat ribbon cable, and in particular to a resilient carrier apparatus which reduces the length of the flat cable used in the clockspring's design.
Clocksprings are typically used in applications such as connecting an air bag, mounted in the steering wheel of an automobile, to sensors mounted within various locations of the automobile.
For example, U.S. Pat. No. 5,061,195 (1991), issued to Bolen, discloses a type of clockspring which provides a direct electrical connection between relatively movable members in the steering apparatus of an automobile. In this type of clockspring construction, a ribbon cable is used to provide the electrical connection. The ribbon cable is constructed of conductive material which is sandwiched between two layers of mylar. The cable is loosely accommodated in a coiled state within the clockspring's housing. In addition, one end of the cable is attached to the clockspring's stationary member and the other end of the cable is attached to the clockspring's rotatable hub.
In operation, the ribbon cable will either wrap or unwrap around the hub when the hub is rotated. Correspondingly, the length of the cable determines how many times the hub can be rotated. However, a long cable length can result in a higher cost to assemble the clockspring. In addition, a longer cable length can cause the clockspring to have a larger overall mass. Also, a longer cable length can cause more vibration and noise to be generated as the cable is moved within the clockspring housing.
Many devices have been proposed in order to reduce the length of the cable used in the design of the clockspring. However, these devices are not capable of simultaneously and substantially reducing the cable length, the mass of the clockspring, and the level of vibration and noise generated by movement of the cable.
For example, it is known in the art to have a clockspring construction which decreases the length of cable needed because the cable has a U-shaped portion that will move at an angular speed which is less than that of the hub. It is also known to have a C-shaped carrier assembly which has rollers mounted thereon.
One problem with the prior art clocksprings is their inability to provide a means for effectively preventing vibration and noise from being generated by that portion of the cable which is not pressed against the hub. The loose portion of the cable will vibrate and generate noise unless it is made of sufficiently rigid material so that it effectively presses itself against the inner peripheral surface of the housing. However, such a rigid cable will cause the clockspring's reliability to be reduced due to the destructive flexing caused by the reversing of the cable's direction at the turned-back portion.
Likewise, the prior art clocksprings also fail to effectively press both of the carrier assembly's end rollers against the hub. The end rollers are the most critical in ensuring the effective securement of the cable to the hub. However, the carrier assembly's end rollers are secured only by the weak end portions of the C-shaped spring.
In addition, the prior art clocksprings also fail to significantly reduce the cost involved in the clockspring's manufacture. Although the clockspring design reduces the cable length, it also requires the additional expense of providing a carrier assembly consisting of a plurality of cylindrical units which have rollers and are interconnected via a wire spring.
Therefore, a clockspring assembly is proposed having a low cost resilient flat cable carrier apparatus which reduces the cable length and effectively prevents the cable from vibrating and generating noise.
In view of the above, it is an object of the present invention to provide a resilient flat cable carrier apparatus which reduces the necessary cable used to construct a clockspring assembly.
A further object of the present invention is to provide a resilient flat cable carrier apparatus which reduces the overall mass of a clockspring assembly.
An added object of the present invention is to provide a resilient flat cable carrier apparatus which reduces the manufacturing cost of a clockspring assembly.
It is also an object of the present invention is to provide a resilient flat cable carrier apparatus which reduces the vibration and noise generated by a clockspring assembly.
Another object of the present invention is to provide a resilient flat cable carrier apparatus which enhances the reliability of a clockspring assembly.